A light emitting device based on a semiconductor is made by stacking semiconductor layers such as n-type and/or p-type so as to form a semiconductor stacking structure on a substrate and providing electrodes on the layers of different conductivity types, while electricity is supplied through the electrodes so that the device emits light. There is also such a light emitting device comprising a support member and a semiconductor stacking structure made by bonding a semiconductor device structure formed on a substrate onto the support member (for example, shown in FIG. 2 of Japanese Unexamined Patent Publication (Kokai) No. 2003-31858).
However, the structure of the light emitting device of the prior art does not allow it to extract sufficient light, and the electrodes of the light emitting device bonded onto the support member cannot be formed so as have sufficient characteristics suitable for a light emitting device due to constraints of the manufacturing process.
Specifically, in the semiconductor stacking structure that is bonded onto the support member, the electrodes provided on the semiconductor stacking structure before bonding can be alloyed by heat treatment or the like after forming the electrodes, so that the properties of the electrodes such as ohmic property, heat resistance, reliability during the operation of the light emitting device, for example heat resistance of the device and bonding property can be improved. However, the electrodes provided on the semiconductor stacking structure after bonding it onto the support member can not be sufficiently heat treated due to restriction resulted from heat resistance of the bonding member. For example, in case denaturing or deformation of the bonding member through heat treatment causes a decrease in the bonding strength, it is necessary to set a lower heat treatment temperature so as to avoid such troubles. As a result, it has been difficult to obtain satisfactory characteristics of the electrodes that are provided on the semiconductor stacking structure after bonding it onto the support member.
There is also such a problem that the structure and the arrangement of the electrodes in the semiconductor stacking structure are such that shade the emitted light depending on the material of the electrodes, and therefore the electrode structure involves advanced design. In case the semiconductor layers of different types of conductivity have different levels of carrier mobility, layout of the electrodes formed on the semiconductor layers different types of conductivity has a great influence on the control of carrier, consequently on the efficiency of light emission. For example, when the surface area of the light emitting device becomes larger, a part of the light emitting structure section may not emit sufficient amount of light due to the structure of the electrode even when the light emitting structure section has a surface area that is proportional to the surface area of the device. Moreover, the light emitting structure section may instead absorb the light propagating in the light emitting device thus making it impossible to increase the optical output in proportion to the increase in the device area. When the area of light emitting devices, area of the light emitting structure and the number of light emitting structure sections are increased, there arise such problems as the uniformity of light emission and loss of light in a portion having low efficiency of light emission. Therefore, design of the structures of the electrodes and the device are very important.
In case the electrode is used for dissipating heat, it must be designed by giving consideration also to the layout of the lead-out portion of the electrode for external connection and the route of dissipating heat from the semiconductor stacking structure. Thus extremely sophisticated design is required to provide the optimum semiconductor stacking structure and electrode structure.
The semiconductor stacking structure bonded onto the support member also has the following problem. When electrodes of the light emitting device are provided between the support member and the semiconductor stacking structure, strength of bonding with the bonding member or with an insulating film that isolates the electrode of the semiconductor stacking structure and the bonding member, layout of these members within a plane and the stacking structure have importance, and it is necessary to give consideration to the heat treatment of the electrodes and heat resistance of the bonding member in the manufacturing process. Also with regard to the stability of the members used in the light emitting device under the influence of the heat generated during operation of the device, design of the route of dissipating heat from the semiconductor stacking structure to the support member is important for ensuring sufficient reliability in terms of bonding strength and the like.